High precision nano-positioning systems typically use linear actuators to effect positioning at the nano-scale range. Positioning speed and accuracy are determined largely by the type of linear actuators used. It is desirable that such systems have high positioning speed and accuracy as they directly affect the speed and accuracy of nano-manufacturing processes in which they are commonly used.
Various types of nano-positioning linear actuators are currently available, with the most popular one being solid-state piezoelectric (PZT) actuators as they are able to provide a large output force with high stiffness. However, PZT actuators have a limited motion range in the hundreds of microns, which makes them unsuitable for applications where a few millimeters of motion are required. On the other hand, conventional electromagnetic actuators that can provide millimeter motion range have small output force and low stiffness. These typically use conventional roller or ball bearings that introduce backlash and Coulomb friction which affects positioning repeatability, and hence accuracy. Use of notch-type flexure joints instead of mechanical bearings can help to achieve frictionless, wear-free and repeatable motion at high resolution. However, such flexures have a small motion range and possess relatively high stiffness in the driving direction which reduces the maximum output force that can be achieved.
Thus, there is presently no nano-positioning linear actuator available that can offer accurate millimeter displacement with moving speed greater than 100 mm/s and relatively high output force greater than 50N, in order for nano-manufacturing processes to be automated.